Just a sidenote: It's not that hard to do manual focus and when you get used to it, I think you will prefer it over the automatic one. Not really what you ask for, but I just wanted to mention it.
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grmOct 20 '10 at 8:41

The camera makes a best guess as to what it thinks is the primary subject of a photo. Given that the camera has multiple (three) autofocus points, sometimes it guesses wrong. There are a couple ways to overcome the fact that autofocus can't always guess where you'd like the focus point:

Manually choose the correct focus point and compose your scene so that your subject is at that focus point

Use a single focus point (usually the center) all of the time, and set your focus using that point and then recompose your scene.